The present invention relates to a liquid heating apparatus such as a fryer, a noodle boiling machine or the like, and in particular, to a liquid heating apparatus which can effectively heat a liquid in a liquid bath.
Conventionally, a fryer used as this type of liquid heating apparatus has been previously disclosed, such as, for example, the device shown in FIGS. 7 and 8, where the fryer 101 has a liquid bath 103 which is located on an upper portion of a main body 102, and a plurality of exhaust pipes 104 (four in FIG. 7) are arranged in a horizontal state at the substantially central position in a height direction of the liquid bath 103. These exhaust pipes extend penetratingly from one end side 103a (front side of the main body 102) toward the other side 103b (rear side of the main body 102). Each exhaust pipe 104 is provided with connective pipes 105a and 105b which are inclined right and left and alternately extend in a generally cross-shaped configuration in the exhaust pipe 104, at predetermined intervals in a longitudinal direction.
Moreover, a lower portion on one end side 103a (FIG. 8) of the liquid bath 103 is formed with a combustion chamber 109, which comprises a horizontal wall 106, a vertical wall 107, and a cover 108 downwardly extending from the front end of the horizontal wall 106. A gas burner 110 is arranged in the combustion chamber 109. A bottom portion of the liquid bath 103, on the lower portion of the exhaust pipe 104, is inclined so as to become low on its forward side, and a portion just under the bottom portion is provided with a drain cock 111. Furthermore, a waste oil box is arranged at a downward position of the drain cock 111 in the main body 102.
In the fryer 101 of FIGS. 7 and 8, when the combustion chamber 109 is filled with a combustion gas generated by a combustion of the gas burner 110, the horizontal wall 106 of the liquid bath 103 is directly heated so as to heat an oil 113 in the liquid bath 103. Then, the combustion gas flows into the exhaust pipe 104 and through the interior of exhaust pipe 104, as shown by the arrows A, and thus, is discharged from a discharge cylinder 114 to the atmosphere.
In this prior apparatus of FIGS. 7 and 8, four exhaust pipes 104 are arranged in a horizontal state. Therefore, the oil 113 in the liquid bath 103 is heated by the combustion gas flowing through the exhaust pipe 104 while being heated by the connective pipes 105a and 105b located in the exhaust pipe 104. As a result, an upper portion of the liquid bath from the exhaust pipe 104 becomes a high temperature section. On the other hand, a lower portion of the liquid bath from the exhaust pipe 104 becomes a low temperature section. Furthermore, a food is deep-fried in the oil 113 of the high temperature section while being prevented from falling into the low temperature section by a net 115 arranged on the upper portion of the exhaust pipe 104.
However, this fryer 101 of FIGS. 7 and 8 has a construction in which four cylindrical exhaust pipes 104 are arranged at the lower portion of the liquid bath 103, and the exhaust pipe 104 is provided with the totaled six connective pipes 105a and 105b arranged in cross-shaped configuration. For this reason, a heating surface area of the combustion gas flowing through the exhaust pipe 104 is small with respect to the exhaust pipe 104. As a result, it is difficult or impossible to effectively heat the oil 113 of the liquid bath 103 by means of the gas burner 110. Thus, the aforesaid conventional fryer 101 has a disadvantage in that it is difficult to obtain sufficient heat efficiency.
Moreover, a temperature of the combustion gas flowing through the exhaust pipe 104 in the fryer 101 becomes highest at an inlet side on the combustion chamber 109 side of the exhaust pipe 104, and becomes lowest at an outlet side on the discharge cylinder 114 side. In fryer 101, the total of six connective pipes 105a and 105b are merely extended in a diametrical direction of the exhaust pipe 104 and are arranged along the longitudinal direction thereof at substantially constant intervals. For this reason, it is difficult to obtain optimum heat conduction along a temperature gradient of the combustion gas flowing through the exhaust pipe 104. As a result, there is a disadvantage in that a temperature difference is formed in the oil 113 in the longitudinal direction of the liquid bath 103. In addition, a pressure loss results in an exhaust pipe 104 section forming a heat exchange section, and the outer dimension of the exhaust pipe section must be inordinately large. For this reason, it is difficult to perform cleaning or maintenance.
The present invention has been made taking the aforesaid problems in the prior art into consideration. One object of the invention is to provide a liquid heating apparatus that can obtain sufficient heat efficiency by providing a large heating surface area by way of combustion gas flowing through an exhaust pipe located in a liquid bath and by preferably passing the combustion gas therethrough.
A further object of the invention is to provide a liquid heating apparatus which can obtain sufficient heat efficiency and can uniformly heat a liquid in the liquid bath.
Still another object of the invention is to provide a liquid heating apparatus having simplified heat conduction fins so as to provide the apparatus at a low cost.
To achieve the above objects, the present invention provides a liquid heating apparatus that includes: a liquid bath; a combustion chamber which is provided with a burner and is formed at one side on a lower portion of the liquid bath; and an exhaust pipe which is located substantially horizontally in the liquid bath and which extends from one side of the liquid bath toward the other side thereof and thus heats a liquid in the liquid bath by passing a combustion gas generated in the combustion chamber through the exhaust pipe. The exhaust pipe is preferably of a tubular shape having a vertical side wall with a fin integrally located on an inner surface of the side wall of the exhaust pipe along a longitudinal direction thereof.
With the above construction, the combustion gas generated by the combustion of the burner flows into the exhaust pipe from the combustion chamber and then flows through the exhaust pipe so as to heat the fins which are integrally fixed to the inner surface of the exhaust pipe during the passage of the combustion gas. The fins serve to substantially enlarge the heating surface area of the combustion gas with respect to that of the exhaust pipe, and the fins are located on the inner surface of the side wall or wall of the tubular exhaust pipe. Therefore, heat-exchanged combustion gas is not confined in the upper portion of the exhaust pipe by high temperature combustion gas from the burner, so that this combustion gas can be preferably passed through the exhaust pipe. As a result, heat exchange is preferably performed over the entire region of the longitudinal direction of the fin or fins. The heat of the fin is thus more effectively transferred to the exhaust pipe so that liquid around the upper portion of the exhaust pipe is more effectively heated and sufficient heating efficiency is obtained.
Further, the invention preferably provides the liquid heating apparatus wherein the fin has a heating surface area which is predetermined in accordance with a temperature gradient in a longitudinal direction of the exhaust pipe. With the above construction, for example, the height of the fin is lower at an inlet side of the exhaust pipe, where the combustion gas temperature is high, and is higher at an outlet side of the exhaust pipe, where the combustion gas temperature is low. Thus, the heat energy of the combustion gas can be further effectively transferred to the exhaust pipe by way of the fin or fins. As a result, improved heating efficiency can be obtained.
The invention also preferably provides the liquid heating apparatus wherein the fin is formed with a generally U-shaped cross section and is fixed to the inner surface of the exhaust pipe at a predetermined interval.
The invention also preferably provides the liquid heating apparatus wherein the fin can be formed into a generally L-shape cross section, and the fin is fixed to the inner surface of the side wall of the exhaust pipe. With either of the above constructions, the fin has a U-shaped or L-shaped cross section and therefore its shape is greatly simplified and fixed to the plate at predetermined intervals, thereby making it less expensive to manufacture the exhaust pipe and thus providing a liquid heating apparatus at low cost.